It is only a matter of time before weeds make their way into your lawn. Although normally green in color, they typically make a lawn look unkempt or patchy. To return to the days when you had a healthy lawn, you can try a number of things. First, it is best if you find out what kind of weed you have so that you can better fight it. While fighting the weeds, your lawn will benefit from the extra care and grow thicker.
Pull up tall weeds that might be growing in the grass. A lot of weeds have deep roots and pulling them up won't do any good. If you pull them and they come up easily, more than likely you got the entire weed.
Overseed in the fall with a noninvasive grass like rye. Rye doesn't overtake a lawn, but adds to it. The thicker your grass, the less room there is for weed seeds to work their way through.
Raise or lower the mower blades. Depending on the type of weeds in your yard, you can adjust the blade height to a level that is still okay for your type of grass, but not optimal for the weed. This will discourage continued growth. You can use the same method with watering and fertilizing. Use more or less so that the weed is discouraged, but keep the levels within acceptable limits for the grass.
Look for reasons the weed is growing. Some weeds are encouraged by the condition of the soil. Aerating or adjusting the pH balance might discourage growth. Each weed is different. If you can't identify the weed in your yard, take a sample and go to a landscaper, extension office, greenhouse or another expert for identification. After you know the type of weed you are dealing with, you can find out what it doesn't like.
Apply a product that kills weeds and does not hurt grass. These are referred to as selective postemergence herbicides.